Drilling is an important part of PCB contour processing, in which bit selection is very important. In between the drill and the knife body connect high strength and welding hard alloy drill, machining surface roughness, aperture good tolerance, high position precision hole. When the screws are tightened, the crown can achieve the same amount of feed as the welded drill.
For end users with hard alloy cutting bit four basic forms: select the whole hard alloy, cemented carbide indexable inserts, welding drill and removable hard alloy drill. Each has its advantages in a particular application.
The first monolithic carbide drill was used in modern machining centers. These self centering drills achieve excellent chip control and chip removal in most of the workpiece materials due to their specially designed cutting edges. The integral carbide drill has a self centering geometric angle and a good accuracy to ensure high quality holes without any further processing.
The bore of the welding bit has a high surface finish, a high dimensional accuracy and a good position accuracy, without further finishing. Because of the cooling hole, the drill bit can be used for welding processing center, CNC lathe or other sufficient stability and speed of the machine.
Finally, a bit form steel knife body and a removable solid carbide drill is called the crown together. The drill provides higher productivity at lower processing costs under the condition of providing the same accuracy as the drill bits. The new generation drill with a carbide crown provides precise dimensional increments and has a self centering geometric angle that guarantees high machining accuracy.
Consider tolerances and machine tools carefully
The factory shall select the drill according to the specified tolerances. Usually, small bore tolerances are tighter. As a result, the bit manufacturer sorts the drill bit by specifying nominal bore size and upper tolerance. In all bit forms, the overall hard alloy drill is the most tight. This makes them the best choice for drilling holes with extremely tight tolerances.
These drills are often a good choice for drilling, processing, and processing. Indexable insert drill bit is the industry doing heavy work. This means that the end user needs in the hole with greater tolerances can be used when the indexable insert drill, otherwise they must prepare the finishing hole with boring cutter. Together with the tolerance of the hole, the factory needs to consider the stability of the machine during the selection process. Because of stability, the tool life and drilling accuracy are guaranteed. The factory shall verify the status of the spindle, jig and attachment of the machine. They should also consider the inherent stability of the drill bit. For example, the monolithic carbide drill provides the best rigidity, which allows it to achieve very high accuracy.
Indexable inserts, on the other hand, are prone to deviation. These drills are fitted with two blades - an inner blade at the center and a blade that extends outward from the inner blade to the edge - initially with only one blade. This creates an unstable condition that causes the cutter to deflect. And the longer the bit, the greater the deviation. This high stability cutting design allows the drill to enter the workpiece at full speed of feed. The only exception is that when the bit and the machined surface are not vertical, it is recommended to reduce the feed from 30% to 50% while cutting in and out.
The steel drill bit permits slight deviation so that it can be successfully applied to the lathe. The hard, solid cemented carbide bit may easily break, especially if the workpiece is not properly centring. Don't neglect the problem of chip shavings in many factories. In fact, chip rejection is the most common problem in drilling, especially in the manufacture of low carbon steel. And what kind of drill should we use?. Always check manufacturer recommended coolant minimum flow level. At lower flow rates, it may be necessary to reduce the feed rate. Check life cycle cost, productivity, or cost per hole is the biggest trend that affects drilling today. This means that drill manufacturers must find ways to combine certain operations and to develop drills that can accommodate high throughput and high speed machining.
The latest bits with interchangeable carbide tips provide superior economics. Instead of replacing the entire bit cutter, the end user only buys the carbide cutter head at the price equivalent to the regrinding of a welded bit or an integral carbide bit. These crown changes are convenient and precise, and the factory can use a number of crowns on a bit cutter to drill several different specifications of the empty space.
In addition, it eliminates the need to back up the drill bit when regrinding the drill bit or the whole carbide bit. The factory should also take into account the overall life of the tool when examining the cost of each hole.
There is also a productivity problem here. Welding bit or whole carbide drill must be regrinding; therefore, the factory tends to reduce speed to avoid sticking. But the tool bit can not be regrinding, so the factory can use sufficient feed speed and speed without worrying about cemented carbide.